Regenerative furnace.



N. F. EGLER.

REGBNERATIVE FURNACB.

APPLIOATION FILED MAY 1. 1913.

Patented Nov. 25, 1913.

N. F. EGLER.

REGBNERATIVB FURNAGE.

APPLIOATION FILED MAY 1, 1913.

1 ,079,642. Patented Nov. 25, 1913. f

3 SHEETS-SHEET 3.

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NICOLAS FRIDERICH EGLER,

OFTCHICAGO, ILLINOIS, ASSIGNOR TO TI'IOMAS S. BLAIR, JR., F CHICAGO, ILLINOIS.

REG-ENERATIVE FURNACE.

Specification of Letters Patent.

Patented Nov. 25, 1913.

Application mednay 1, 1913. serial No. 764,925.

v in the specification and shown in the accompanying drawings, in which:-

Figure 1 is a longitudinal section on line 1 of Fig.- 2 through an open-hearth furnace embodying my invention; Fig. 2 is a diagrammatic plan view showing the furnaceproper and its operating connections includ-v ing the regenerators, piping, valves and stack; Fig. 3` is a section on the line 3 of Fig. 2 showing the gas-valve, and Fig. 4 is a section on the line 4 of Fig. 2 showing the air-valve.

Referring to the drawings, 5 is the combustion chamber of the furnace into which open gas-ports 6 and 7 connected to downtakes 8 and 9 in accordance with common practice. Above the gas-ports, and separated therefrom by the usual gas-port covering, are air-ports 10 and 11, connected with downt-akes 12 and 13. As far as-the present invention is concerned, t-he construction of these ports is immaterial but I have shown ports of the Blair type for the reason that that construction has now been established to be most satisfactory, involving as it does, an impervious barrier between the gas and air ports in the form of a metal box forming the entire gas-port covering.

The gas-downtakes communicate with gas-regenerators 14 and 15 and the airdowntakes 12 and 13 communicate with air regenerators 16 and 17, in accordance with common practice. The opposite ends of the gas regenerators open into gas-conduits 18 and 19, and of the air regenerators into airconduits 20 and 21.

22 'is the stack which communicates, in accordance with common practice, with a passage 23 lying between the ends of the gas and air conduits, so that access to it may be controlled by the reversing valves.

24 is the usual gas-main .running to the gas-house, if the furnace be one adapted to be run on producer gas. If the furnace be one adapted for natural and notfor producer gas, this pipe will be omit-ted.

25 is a box into which the gas-main enters and, if the furnace be a natural-gas furnace, this box or something serving a similar purpose will be used in accordance with my invention.

26 is the gas-reversing valve and 27 is the air-reversing valve, these valves being shown of ordinary form, performingthe ordinary functions of similar valves, that is, at will, throwing the regenerators atvone end of the furnace into communication with the stack through the passage 23 and the air and gas regenerators at the other end, respectively, into communication with the atmosphere and the box 25 opening into the gas-main.

The parts thus far enumerated are of ordinary construction and it will be understood that they. may be modified to any extent desired within the limits set by approved practice.

28 and 29 are pipes through which cokeoven gas may be admitted to the two gas ports.

30 is a by-pass through which the products of combustion in the furnace may be conducted from the outlet end of the furnace back to the gas-port or parts communieating therewith, a pump 31 being interposed in this by-pass to secure the proper draft. In the preferred embodiment of my invention this by-pass leads from the conduit 23 leading to the stack. or from the stack proper, if the construction be thereby rendered more convenient, to the space -above the gas-reversing valve, or more broadly speaking to the intake-end of the gas-reversing valve. When the furnace is one equipped for producer gas the by-pass may open, as here shown, into the box at the end of the gas-main, or into the gas-main proper, while if the furnace be one equipped for natural gas where there is no gas-main, a box or other receptacle will preferably be provided on the intake-end ofthe gas-reversing valve to receive the discharge from the by-pas's 30, as-shown in Fig. 3, the main 24 being omitted.

The present furnace vis designed particuthe air-blanket.

excellent fuel and its use usually involves no peculiar problems. The special requirements of the open-hearth furnace, however, are such that the use of coke-oven gas, in accordance with prior practice, has been most unsatisfactory. It is, of course, well known that the flame in an open-hearth furnace is so hot that vif permitted directly to impinge upon the roof, it would burn or melt a hole through the roof very promptly. The roof is saved from destruction only by the fact that the air spreads out and blankets the roof, thereby cooling the roof, with reference to the llame beneath it, and also, holding the flame down in the most efficient position for its work on the bath. Any condition which causes the flame, in its travel across the furnace to rise and penetrate this protecting air-blanket results in destruction of the roof, and produces a consequent inefiiciency of the furnace as well asan increase in the cost of repairs. Heretofore in the use of coke-oven gas in regenerative furnaces, it has been found that this protecting air-blanket was penetrated by the flame to a much larger extent than with other fuels and therefore the roof has been very short-lived. In addition, the flame has been of an unsatisfactory and uncontrollable character so that the heat units were not used to the best advantage and a larger number of heat-units per ton of steel were required than with other and more controllable fuels.

It is probable but not certain that the rise of the flame to the roof results from several causes, among which the following may be suggested: In the first place the coke-oven gas, by reason of its extreme lightness (it is usually about half hydrogen), rises through the air-blanket to a much greater extent than the heavier natural or producer gas. Coke-oven gas also seems to burn very close to the port therefore developing a large amount of heat very suddenly, almost explosively, whence it expands rapidly close to the port and so forces its way into Certain it is that cokeoven gas burns with a brush-like scattering flame. The cause of the early and scattering flame with coke-oven gas, under these peculiar conditions prevailing in the openhearth furnace, is probably due to a rather complex combination of causes which it will not be desirable to discuss here. Whatever may be the cause, it is an undoubted fact that coke-oven gas produces a very unmanageable flame which not only rapidly deteriorates the roof of the furnace in which it is used, but which expends its heat most inefficiently upon the metal in the bath. The inefficiency of the furnace would, of course, follow as a corollary from the fact that heat is wasted in melting down the roof.

Efforts have been made to mix coke-oven gas with air in the port as is commonly done with natural gas, but while this results in a heavier mixture, the combustion of the cokeoven gas with that part of the air which it. meets in the gas-port is so thoroughly under way by the time the furnace chamber is reached that the flame scatters very badly. It will be observed that these problems are peculiar to furnaces of the character herein described, that is, practically open-hearth or other reverberatory regenerative furnaces which run to the extreme temperature used in such furnaces and where the roof is saved from destruction only by a protecting blanket of air whose substantial continuity must be preserved from end t0 end. By my invention I have remedied these difficulties and produced in the open-hearth furnace a coke-oven gas flame which is thoroughly controllable. This is done by mixing the coke-oven gas in the gas-ports with the inert and relatively heavy burnt gases.

The following table shows the specific gravity and the heat-units of coke-oven gas, producer-gas, stack gas from a coke-oven gas furnace, and of certa-in mixtures of cokeoven gas with stack gas.

Specifcamv- B. T. U. per

ity (ar=1). cu. tt.

coo 150 1, 100 o It will be seen from the foregoing that it is very easy to obtain a mixture of cokeoven and stack gases having exactly the heat-units and practically the specific gravity of producer gas which has long been known to be thoroughly efficient and economical for its intended purpose. Such a mixture issuing from the port obviously burns practically as does producer gas. It should be added that for ordinary fuel purposes the mixture so produced would probably be of little value. Its present utility lies not in its inherent qualities as fuel gas, but in the fact that it produces a flame which is controllable and efficient under the peculiar conditions of the regenerative furnace.

In the use of my furnace when running on coke-oven gas, the gas-main iscut off from course not chemically united) with the cokeoven gas, thence into the furnace where the mixture is burned, thence through the opposite ports, the regenerators and into the stack, a small part being lwithdrawn to be returned al second time into the furnace.

The present arrangement is the preferred one for the reason that it is desirable in every plant to have some other fuel supply than coke-oven gas alone. The construction of any furnace in which coke-ovengas was the sole possible fuel would be most unwise. The present ,construction is one which can be used with producer gas or with natural gas without substantial change. For producer gas, the by-pass 30 will be closed, the coke-oven gas pipes will be closed and the furnace will run in the ordinary way. It is an advantage of the present construction that the stack gas is considerably cooled in the outgoing regenerators and heated up again in the opposite gas regenerator, thus passing through thepump 3l in a relatively cool condition. It will be evident, however, that theoretically the gas might be taken direct from one gas downtake to the other,- without passing through the regenerators at all and the gas regenerators could be omitted, but under such conditions the gas would necessarily pass through the pump yat a terrific heat and it might not be possible to o-btain a pump which would do the work satisfactorily'and also the furnace could then be used with no other fuel.

The point at which the coke-oven gas enters the stream of stack gas on its way to the gas-port is immaterial, since the stack gas is Wholly inert and no chemical reaction but only a physical mixture occurs between the two components. The coke-oven gas should enter the stream far enough from the mouth`of the port to be thoroughly mixed and to acquire a perfectly definite movement before passing the nose of the gas-port arch. For reasons largely of convenience of construction, I have introduced the gas at the rear end of the gas-port as shown, but it could be otherwise introduced if desired.

lVhat I claim as new and desire to secure by Letters Patent is 1. A regenerative furnace provided at each end with gas and superposed air ports and having means to return burnt gas issuing from one end of the furnace and without chemical change thereof to the gas-port at the opposite end, andmeans to introduce coke-oven gas into the burnt gas so returned.

2. A regenerative furnace provided at each end with gas and superposed air ports and having a conduit leading from a burntgas passage on the outgoing end of the furnace to a passage leading to the gas-port at the opposite end, a pump in said conduit, and means to mix coke-oven gas with the burnt., gases passed through said conduit.

3. In combination, a regenerative furnace proper having at each end gas and super# posed air ports, regenerators connected to said ports, a stack to which the regenerators are alternately connected, a ley-pass leading stack-gas to the gas-regenerator on the intake-end, a pumpin said by-pass, and means to mix coke-oven gas with the gas passed therethrough.

4. In combination, a furnace proper having at each end gas and superposed air ports, regenerators connected to said ports, air and gas reversing valves, a by-pass from the exhaust side of a reversing valve to the intake-side of the gas-reversing valve, a pump in said by-pass, and means to introduce coke-oven gas into the burnt gases passed through said by-pass.

5. The process of heating reverberatory furnaces, which consists in mixing a gas containing a relatively high percentage of hydrogen with the burnt gas issuing from the furnace, without change of the chemical constituents of such burnt gas from the condition in which it so issues, and discharging said mixture into the furnace beneath' asuperposed stratum of air.

In testimony whereof I have hereunto set my hand this 24th day of March, A. D. 

